Shock mounted instrument



Junezo 1.9444 v. L. WEAVER SHOCK MOUNTED INSTRUMENT I `2 sheets-sheet 1Filed Nov. 7, 1942 Jun 20,1944. v, L 'wr-:AVER

SHOCK MOUNTED INSTRUMENT Filed Nov.v 7. 1942 2 sheets-.sheet 2 Invntor:Vivgglv l We aven His tto'r'neg Patented June 2o, 1944 SHOCK MOUNTEDINSTRUMENT Virgil L. Weaver, Lynniield, Mass., assignor to GeneralElectric Company, av corporation of New York Application November 7,1942, sei-iai No. 464,906 4 Claims. (Cl. 248-27) My invention relates toinstruments mounted to withstand shocks.

An' object of my invention is to provide delicate instruments capable ofwithstanding severe shocks or sudden accelerations of supporting panels.It is an object of my invention to provide mountings for taking up shockas distinguished from merely absorbing or damping out vibrations. Anobject is to provide arrangements for producing relatively greatdisplacement of an instrument with respect to a supporting panel whilethe instrument is being accelerated in, order to follow the movement ofthe panel.

Other and further objects and advantages of my invention will becomeapparent as the description proceeds.

In carrying out my invention in its preferred form I provide acushioning or padding member or unit for mounting a delicate instrumentor the like in a housing or between confining members rigidly secured toa panel or other supporting structure, which is secured to flooring orother framework, through which very severe shocks analogous to hammeriblows may be transmitted as a result of impacts applied thereto byexplosive or other action. The cushioning or padding unit is composed ofresilient material such as molded rubber composition or the like formedwith a honeycomb or cellular structure, which permits a relatively greatdisplacement to occur between theinstrument to be protected and thesupporting panel upon the initial impact of the shock to the panel. Thishoneycomb structure furthermore provideslfor: transmission of acceleration from the panel to the instrument at a rate depending upon theextent of the relative displacement; acceleration of the instrument tothe velocity of the panel before the limit of relaa tive displacement isreached; sulciently gradual application of acceleration to preventdamage to the instrument, and yet increase of acceleration to asucientintensityin case of severe shocks. Damping is provided to preventvibration and reduce overshoot.

A better understanding of the invention will view corresponding to Fig.1, showing another embodiment of my invention with a round-caseinstrument instead of a square-case instrument; Fig. 5 is a fragmentaryface view of the apparatus of Fig. 4, with a portion thereof broken awayto expose the interior construction; and Fig. 6 is a fragmentaryperspective view of the apparatus of Figs. 4 and 5, seen from the rear.Like reference characters are used throughout the drawings to designatelike parts.

An arrangement in accordance with my invention for mounting asquare-case instrument to be resistant to shocks or sudden impacts uponits supporting panel is illustrated in Figs. l to 3. 'I'here is shown aninstrument in a square case I I (having rounded corners I2), with aresilient mounting or cushion unit I3, and a supporting panel I4,represented only in part. It will be understood that the panel I4 restsupon flooring or framework (not shown) to which it is preferably madefast. My invention is not concerned with the particular type ofinstrument to be mounted on the panel I4. It maybe a. delicate deectingpointer moving element electrical measuring instrument, a relay, a meteror any device which must be securely mounted, but4 is not itself capableof withstanding severe shocks, violent impacts or sudden accelerations,to which the panel. I4 may be subjected directly or by forces applied tothe framework or ooring (not shown) supporting the panel I4. In view ofthe rough treatment which the panel i4 may be assumed to receive, it isrepresented as being composed oi a high-strength material, such as steelplate.

The square instrument case II is shown as 4being of the conventionaltype designed for flush mounting on a panel and having a ange I5,

' which would normally rest against a mounting be afforded by thefollowing detailed description considered in connection with theaccompanying drawings. 'I'hose features of the invention which arebelieved to Ibe novel and patentabley are pointed out in the claimsappended hereto. In the drawings Fig. l is ka side view, partially invertical cross-section of one embodiment of my invention; Fig. 2 is afragmentary cross-sectional -view of the portion of the apparatus cut bythe plane 2-2 of Fig. 1; Fig. 2 a is an voutline diagram of a part ofthe section of Fig. 2; Fig 3 is a perspective view of a portion of theapparatus of Fig. 1, disassembled to expose the interior and show theinternal construction; Fig. 4 is a panel along the edges of aninstrument-receiving opening in the panel. The casing II has a removableback cover I6 with a slightly raised rim Although the instrument case IIneed not be arranged with its face (usuallywith a transparent window)visible from the front of the panel, the apparatus is described withthis arrangement assumed for the sake of illustration and convenience inexplanation.

The instrument is arranged with its-face I8 (see Fig. 5), usually with atransparent window (not visible in the view presented by Fig. 1), ex-yposed at the front of the panel I4, which is the right-hand side of thepanel as shown in Fig. 1. The instrument casing II is shown withelectrical terminal screws lI9 extending from terminal studs 20,projectingjrearwardly through the back coverIB., y a f Instead ofsecuring the instrument case II directly to the panel I4, as might bedone in the case of a panel not 'liable to shocks and violent impacts,the cushion unit I3 is provided, into which the casing II is fitted anda housing or set of confining walls is secured to the panel I4 which thecushion unit I3 fits.

For better supporting the rearwardly extending terminal screws I9 andtaking up forward and backward relative displacement between theinstrument and the panel I4, there are provided a terminal supportingmember such as a yoke 26 or U-shaped bracket and resilient or cushioningbushings 21. The yoke 26 is secured tothe panel I4. For example, asshown, it may have ends attached, as by`welding, to the horizontalplates 2| and 22. The bridge portion 28 of the yoke 26 has openings 29,through which the terminal screws I9 are adapted to pass. The bushings21 t in the openings 29 around the terminal gscrews I9. 'They arecomposed of suitable insulating and resilient material, such as moldedrubber composition, for example. As shown the bushings 21, each consistof a sleeve portion 30 having an integral center enlargement or circularrib 3| and end flares 32. The margins of the yoke openings 29 aredished, and dished Washers 33 are provided, which are attachable againstthe lyoke 26 for securing the bushings 21 in the yoke openings 29bycIamping the bushing ribs K3|. Nut-backed Washersv 34 are mounted onthe terminal screws I 9 to provide abutments or stops for the end ares32 of the bushings 21, to control and limit the back and forthdisplacement of the instrument casing I3 with respect to the panel I4and the yoke bridge 28. The bushings 21 do not in themselves constitutemy invention,

and they may be of the type knownas Lord mountings.

The novel construction of the cushion unit I3 the front and back coversof the casing II. As formed. the four corner portions 43 of the strapportion 31 or liner are made short to form straight may be perceivedmost clearly from Figs. 2 and 3. l

It is shown molded as an integral unit including cellular or honeycombpad portions 35, a face, or window-frame portion 36, and a strap orliner portion 31. The unit I3 may be composed of any suitable resilientmaterial having the requisite strength and elasticity in tension, shearand compression, such as molded rubber composition.

The pad portions are honeycombed, i. e., they are of such cellularstructure as to form in effect two or more rows of blocks arranged incheckerboard fashion, with the blocks in one row opposite spaces betweenblocks in the adjacent row, and with a wall or membrane between adjacentrows of blocks to unite the structure and yield in tension as will beexplained more in detailhereinafter. Thus in the enlarged fragmentaryoutline diagram, Fig. 2a, representinga portion diagonals as shown inFig. 3, which are stretched whenv the instrument casing is inserted tothe rounded square cornershape shown in Fig. 2, for more secureattachment to the instrument casing. It will be observed that the liner31 is shown as integral with the adjacent block portions of the padportion 35 of the cushion unit.. The window-frame portion 36 of thecushion unit serves to close the gaps between the instrument face I8,and the edges of the panel opening 5.

Friction plates or slide plates 44 are providedV to which the outersurfaces of the outside row,

of blocks of the pad portions 35 of the cushion unit are bonded.. Forinsuring permanent attachment of the slide plates 43 to the cushionunit, the plates 44 are provided with punched tongues 45 and thesetongues are Placed as inserts in thecushion unit I3 at the time it ismolded. The cushion unit I3 is placed on the casing II by stretching theliners 35 and 43 sufciently to allow the cushion I3 to slide over thesupporting rim I5 or I6. It will be understood that to facilitateinsertion of the casing II into the cushion unit I3, the raised-rim backcover I6 may be removed temporarily.

When the panel I4 is subjected to al violent impact it is highlyaccelerated and starts to move abruptly, but, by reason of my mountingarrangement the instrument is more gradually accelerated. Before theinstrument casing II has been driven against one ofthe cushion confiningwalls 2I-24, its velocity has been brought up to that of the panel. Uponreturn motion, if any, of the panel the same action takes place. Someinitial acceleration is transmitted to the instrument by the slidingfriction between at least one pair of the slide plates 44 and theadjacent confining plates 2l-24, regardless of the direction of relativedisplacement. This initial acceleration is proportional to the amount offriction between the instrument and the panel, whereas the accelerationproduced by compression of the rubber supporting member is proportionalto the relative displacement of the instrument and the panel. Therefore,the supporting member can impart acceleration to the instrument onlyafter the panel has moved a nite distance, whereas the friction plates"apply acceleration to the instruwise or right and left along the' planeof the panel,I and back and forth perpendicular to the plane of thepanel. In the case of back and forth motion, perpendicular to the panel,the relative displacement is taken up by the bushings 21 and such motionis damped out by the friction'of all four slide plates 44, sliding alongthe plates In case of up and down or sidewise motion parallel to thepanel I4, the cushion unit I3 functions to take up relative displacementand either the side friction plates slide along the plates 23 and 24 todamp out overshoot or the top and bottom friction plates slide along theplates 2| structure of the cushion unit I3 causes it to permit largerelative displacement of the panel and the instrument casing withoutabrupt stoppage at the physical limits of the permitted relativedisplacement. In fact such physical limits are never reached becausetheinstrument case is brought up to the velocity of the panel before thepad portion 35 of the cushion unit I3 `has been compressed` an amountapproaching the limit.

t The action of the honeycomb structure in permitting large relativedisplacement, and gradual acceleration of the instrument, but bringingit up to the panel velocity before the honeycomb is fully compressed maybe seen by analyzing the structure. Theinitial impact setting the panelin motion, causes (l) an initial acceleration caused by the frictionplates and (2) the commencement of a relative displacement between theinstrument casing and the panel, starting to squeeze one of the padportions 35 of the cushion unit I3 between the instrument casing wall 42and one of the confining plates, e. g., the plate 23. First the membraneor portion of the cushion unit along the dotted line 40 (Fig. 2a) tendsto be stretched or put in tension with the bridge portions 4I in shearor in bending stress. This causes the application of a small force ofacceleration to the .instrument case which increases steadily, however,as the tension along the line 40 increases with increased relativedisplacement. Then if further relative displacement occurs the blocks"3B of one row tend to squeeze into the spaces 39 between the blocks v33of the adjacent row of b1ocks." This produces wedging action, requiringgreater force and results in progressively increasing therate ofacceleration of the instrument casing. If relative displacement werecontinued to the point of filling the spaces 39 with the blocks 38, theblocks" :3,352,049y and 22 to damp out overshoot. The honeycomb port forprojecting terminal screws and which are iight enough not to requireindependent resillient supportwith respect to relative displacementperpendicular to the panel, an arrangement may be employed inp-which thecushion unit for taking care of verticall or horizontal shocks alsoserves to transmit accelerations for avoiding shock from impactsperpendicular to the direction of the panel. For example, in thearrangement illustrated in Figs. 4, 5 and 6 a honeycomb cushion unit I3'may be employed having in this case a circular inner opening 46Y toreceive a cylindrical instrument casing II. The requisite controlledlatitude o f movement with respect to motion perpendicular to the. panelI4 is providedj l will be explained more in detail hereinafter. The

cushion unit I3' may be similar to the unit I3 illustrated in Figs. 1 to3 except for the shape of the instrument receiving opening therein. If

ldesired, however, a separate overhanging picture frame or flaredportion 50 may be provided for covering an unsightly gap between theflange I5 of the instrument casing II' and the edges of the opening inthe panel for receiving the instrument. The cushion unit I3' alsoemploys 38 would be stressed in direct compression and even greaterforce would be applied stillv more rapidly accelerating the instrumentand prevent- J ing impact against the instrument' casing. In

practice, however, the relative displacement does not continue this far.The sliding friction of the slide plates 44 along the plates 2I and 22v(in the case of horizontally acting impact) serves to apply a uniforminitial force for gradually accelerating the instrument casing I I uponthe initiation of relative displacement.

The resilient bushings 21 or the Lord mountings" take up back and forthrelative displacement, and aided by the friction of the slide plates 44,accelerate the instrument casing II to bring the velocity of the casingup to that of the panel I4 in case of impact perpendicular to the panelI4. However, this action need `not be as effective as that of thehoneycomb pad portions 35 of the cushion unit I3 functioning in the caseof impacts in a direction parallel to the panel I4. 'I'his results fromthe fact that the panel I4 is weaker with respect to force appliedperpendicularly thereto than with respect to force applied in adirection parallel thereto so that the shock with respect to back andforth direction of the instrument would tend to be less violent thanwith respect to shock in a direction parallel to the surface of thepanel I4.

Although I have described and illustrated a particular embodiment of myinvention in Figs. 1 to 3, it will be understood that my invention isnot limited to the specific detailsillustrated and described. In thecase of .smaller and lighter instruments which need not have separatesupcellularhoneycomb structure previously described in connection withthe cushion unit, but the structure may if desired be simplied as shownin Figs. 5 and 6. In comparing the arrangement of Figs. 5 and 6 withthat of 2A, it will be seen that there are fewer spaces 39 and 39'between the solid portions 0f the cushion unit. On the Iother hand, inthe arrangement of Figs. 4, 5 and 6 one o f the block portions 35' ismade shorter than the adjacent "block" -portions 38, in this mannerproviding a more gradual deformationof the cushion unit until the outersurface 5I of the block portion 38'` comes into abutment with the innersurface 52 of the slide plate 44.

As inthe case of the arrangement of Figs. 1 to 3 slide plates orfriction plates are provided which are bonded to the cushion unit I3'and are preferably further secured thereto by means of molded-ininserts, one of which is illustrated at 53 in Fig. 4. Y

In the arrangement of Figs. 4, 5 and 6, instead of employing separateconning plates 2l to 24 for enclosing the cushion unit,vI haveillustrated an integral shell 54`in the shape of a hollow square whichis secured to the back surface of the panel I4. .For example, a pair ofsupporting blocks 55 may be screwed or otherwise secured to the backsurface of the panel I4 and the shell 54 may be welded or otherwisesecured to the supporting blocks 55. The inner surfaces of the shell 54serve as the friction surfaces along which the slide plates'` 44 and 44'slide for the purpose of aiding initial acceleration and absorbingenergy to damp out possible overshoot.v

For supporting the spring arrangement 41, lugs 56 are secured in theinner corners of the cushion-confining shell 54. '.As illustrated thlugs 56 are welded inposition. Such lugs 56 are provided in each ofthe-four cornersof the shell 54 but for clarity onlyone of them is shownin Fig. 6. Each of the lugs 58 has an opening in which a rod 51 isinserted with ends projecting in either direction from the lug 56. Eachend of the rod 51 carries'a helical compression spring 53. For

4 y transmitting the action of the springs 58 to the cushion unit Il andthus to the instrument casing Il', a pair of limit straps 59 is providedat the upper end of the'shell 54, and a similar pair 'of limit strapsv(not shown in Fig. 6) are provided at the lower end of the shell 54.Each of the limit straps 59 has an opening in the end through which oneend of oneof the spring rods 51 passes and a suitable means 6l) such asan enlarged head, cotter pin, nut, or the like is provided forpreventing the limit strap 59 from sliding olf the end of the rod 51.The helical springs 58 are so dimensioned that the inner ends bearagainst the lugs 56 and the outer ends bear against the limit straps 59and hold them against the bolt heads or nuts 60.

The lengths of the rods 51 are made such that the spacing of each pairof limit straps 59 is just sufficient to cause the limit straps to fitagainst the front and back surfaces of the upper portion (or the lowerportion) of the cushion unit I3'. Preferably, however, the upper andlower slide plates 44 have bent-over wings BI to provide more durableabutting surfaces for contacting the inner surfaces of the limit straps59.

In cas-e of impact to the panel I4 in a direction parallel to itssurfaces relative displacement between the instrument casing Il and thepanel I4 is permitted and such relative displacement is taken up by thehoneycomb structure cushion unit I3' in the manner described inconnection .with Figs. l to 3. In case of impacts perpendicular to thesurface of the panel I4 relative displacement between the structure IIand the panel I4 is permitted by the resilience of the 'springs 58, andalso by axial resilience between surfaces 6I and 63, Fig. 6 (rubbermember I3 in tension). Thus, the .instrument casing II' secured in theinner opening 46 of the cushion unit I3.' is allowed to have adisplacement relative to the panel I4 by the compression of all thehelical springs 58 on one side of the lugs 56 and the sliding of therods 5'! through the openings in the lugs 56. For example, if the panelI4 starts to move backward, the shell 41 also starts to move backwardcarrying the lugs 56 backward and compressing the rearward springs 58and causing the front limit straps 59 to bear against the frontbent-over wings 6I of the slide plates 44. The spring force, togetherwith the slide plate friction gradually accelerates the cushion unit I3and the instrument casing I I' so that the instrument casing II isgradually brought up to the velocity of the panel I4. V

In order to insure secure'nent of the instrument casing I I in theopening 46 in the cushion unit I3', the instrument casing II ispreferably provided, not only with the front flange I5, but

lalso with a removable auxiliary back flange 52.

The flange 62 has ears 63 with openings adapted to receive hollow-endedbolts 64. As illustrated in Fig. 4 the bolts are inserted in theopenings in the ears 63 with the heads bearing against these ears andwith smaller machine screws 65 inserted in corresponding openings in thefront flanges I5 with screwheads bearing against the flanges I5 and withshanks 66 threaded into the internal openings inthe hollow ended bolts64.

I have herein shown and particularly described certain embodiments of myinvention and certain methods of operation embraced therein for the:amistosa CFI purpose of explaining its practice and showing its 4.

application, but it will be obvious to those skilled in they art thatmany modifications and variations are possible, and I aim therefore tocover all such modifications and variations as fall within the scope ofmy invention which are denedin the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A shock mounted instrument comprising in combination a supportingpanel with an instrument-reeciving opening therein, an instrument havingan enclosing casing with terminals projecting therefrom rearwardly, anda resilient mounting, said panel having an opening with two pairs ofrearwardly extending plates secured perpendicular to the panel at theedges of the opening, the plates of one pair being perpendicular tothose of the other, the plates of each pair being parallel to each otherand spaced for the said mounting to t between the plates, one pair ofsaid plates having a rearwardly extending terminal supporting yokesecured thereto, said mounting being composed of resilient matevrial ofhoneycomb structure and having an opening therein iltting the saidinstrument casing, said terminal-supporting yoke having openings throughwhich said terminals pass and bushings composed of resilient materialengaging said terminals and the margins of said terminal openings insaid yoke.

2. A shock mounted instrument comprising in combination a supportingpanel with an instrument opening therein, an instrument having anenclosing casing, and a resilient mounting, said panel having a shellsecured thereto with a wall along the edges of said openingperpendicular to said panel, said shell having lugs secured to the innersurface of said wall, said mounting comprising a honeycomb structurecomposed of resilient material tting within said shell for taking upmotion of the instrument against the shell surface, limit straps againstportions of said honeycomb structure, and springs engaging said lugs andsaid limit straps for taking up motion of .the instrument parallel tosaid shell.

3. A shock mounted instrument comprising in combination a supportingpanel with an instrument opening therein, an istrument having -anenclosing casing, and a resilient mounting, said panel having instrumentconfining members secured thereto along the edges of said opening andextending in a direction transverse to the panel, said mountingcomprising honeycomb-structure resilient material formed to fit withinsaid instrument confining members, and having an opening therein fittingthe said instrument casmg.

4. A shock-resistant mounting arrangement for electrical instruments andthe like having enclosing casings, said arrangement comprisinginstrument-confining at plates arranged to deiine, except at thecorners, a` rectangular opening of greater size than the instrumentcasing, and a honeycomb-structure cushion unit composed of resilientmaterial having. flat plates secured to its outer surfaceswhich havesliding fits with the inner surfaces of said instrumentconfining flatplates, said cushion unit having an opening therein of the size andshape adapted to t the casing on an instrument which is to be mountedfor resistance against shock.

.VIRGIL L. WEAVER.

